Hey all, So I'm posting in here since I think the 3TNV88 engines are pretty popular on mini-exs. Mine is actually on a portable sawmill. Anyways, I (stupidly) filled it up with dirty diesel this week, and the little computer on it started throwing codes almost immediately. The codes I'm consistently seeing are P1668 (rail pressure too high during PRV limp home mode) and P0093 (rail pressure delta value high). I can crank and start the engine just fine (as long as I shut off the ECU for a few seconds), and it runs for about 10 seconds until it starts throwing those two codes again. The engine hiccups, runs for about 5 more seconds, then shuts down. (The service manual says P0093 fault mode is engine shut down, so this makes sense). Anyways, I'm looking for advice on what to look at. I replaced both fuel filters. The secondary/water sep was filthy and had gunk on the 'clean' side, the primary filter looked fine when I dumped it, but I replaced it anyway. I removed and cleaned all the feed fuel lines with compressed air. Emptied the tank and put clean fuel in. Tested the electric lift pump for steady flow and it works. I removed the suction control valve (SCV) from the supply pump and the filter screen on it was clear. I plan on calling the yanmar dealer an hour away tomorrow, but who knows when they'll be able to see it. I'm losing money every hour it's down, so hence I'm hearing looking for more advice. Thanks, John
You should disassemble then checking and cleaning the valve which is PLV = Pressure Limit Valve.
He beat me to it.. Just go to the end of the rail & remove & clean out the overflow valve.. Clean out the rail while your there.. U might have to get someone out to clear the codes.?? or find someone w/ the experience to clear them..
Thanks guys. I have it at a yanmar dealer right now. The techs there have almost no idea what they’re doing, so I’m going to suggest this/do it myself in the lot. I’ve been on the phone a bit with yanmar technical support in GA, and I’ve specifically asked if it would be worthwhile to take the plv valve off to inspect and clean, and they said no. Doesn’t make sense why not.
Hi John Not sure if you have the trouble shooting manual for the Yanmar common rail if you PM me with your mail I will post it to you. Kind regards Uffex
Uffex, thank you. I already have the troubleshooting manual with all the Diagnostic codes if that what you’re referring to. I also bought the service manual for the 3tnv88c. I took the plv off and peaked inside the rail... looks fine. Maybe there’s internal damage. In my mind it’s probably the SCV valve stuck open. With the little computer screen on my sawmill, I can read the fuel pressure in the rail. It takes about 3 seconds to see it climb all the way to max, about 26000psi. Makes me think the scv is stuck open. If the plv was stuck closed, I would expect it to take longer for it to climb to such pressures. I’m going to take the scv off and try cleaning it with some ether or something. Apparently the scv is like $615? What a joke.
Good day John Thanks for the reply and good luck with a fix
A after thought surely the pump has some form of pressure limiting, is it not likely that would be the first moving part to swallow dirty fuel. Kind regards Uffex
I have the scv valve off. If I shake it back and forth, I hear something moving in it. Not sure if that means it’s not stuck.
I believe the suction control valve on the supply pump is the first thing after the fuel filter. It has a screen on the control valve, perhaps particles smaller than the screen have plugged it up.
I would speculate the fuel control valve on top of the high pressure pump would not be functioning properly. This would allow unregulated fuel flow to the high pressure pump. Uncontrolled volume to the pump has no where to go but the rail. The safety valve is not really supposed to hang open. I would replace the FCV and the PLV
Typically when the Pump pressure regulator has an open circuit to engine controller it will set to full on and go over rail relief , might not be a bad idea to check that plug and wires to ECU. Also ohm the valve to check for open circuit.
That's what I'm thinking. The engine manuals call it the SCV (suction control valve), which I think is the same as what you're saying, the fuel flow regulator.
.....in the manual; it's called SCV ( S uction C ontrol V alve) or MPROP ( M agnetic PROP ortional Valve) sometimes!!! As you can see in the image below. We need to check five items (in order from easy to difficult). Air instrusion... SCV mechanical elements. SCV drive circuit system. RAIL PRESSURE SENSOR SYSTEM (sensor, wiring...)!!
I just re read your initial post. You had crud on the clean side of the fuel water separator? How about going to the high pressure pump, was there debris there? Did you find anything when you removed the SCV? I would once again remove the SCV. Crank the engine over a bit to flush any debris or water out of that pump. If possible plug it in while cranking. See if the valve inside is shuttling. Then put her all back together and see how it behaves.
1. I've checked for air intrusion. I don't see any air bubbling in the fuel/water separator bowl (it's transparent) while the engine is running, so I'm confident there's no air entering. 2. SCV mechanical elements... what does this mean? The mechanical functioning of the valve? Can I bench test this? The valve does not appear disassemblable. 3. SCV drive circuit system... I'm guessing this means the wiring and the ECM pulse width modulating the valve. I'm confident that is not a cause, as this issue directly originating after contaminated fuel. 4. Rail pressure sensor... I don't think it's this, as I do see fluctuations in the fuel rail pressure on the little computer (they could be wrong, but it doesn't seem likely). I did remove the SCV. The screen on it looked clean. I didn't see anything inside the supply pump. What do you mean 'plug it in while cranking'? Like, start cranking with it unplugged and out of the supply pump, then plug in the wiring during crank to feel if the electromagnet is doing anything? The yanmar dealer looked up the valve and quoted like $615. Such a joke. I just ordered one online from europe for $120, and it should be here early next week with DHL.
With the scv plugged in and removed from the pump, observe it while someone else cranks the engine. You should see or feel a reaction from the pwm.
Just got a call from the yanmar dealer. The yanmar 50's excavators have the same scv. They popped it out of there, tried it on my engine and it's running good again! Phew.
Fortunately was able to find the bosch part number for the scv: 1462C00983 . Ordered through a supplier in Europe, came to $123 with 2-3 day DHL shipping vs the dealer's $615...
Congratulation!! By the way, what is SCV damaged ?? According to your opinion, John.
SCV test for your reference.
Theory is water in the fuel probably damaged the lubrication in the valve. I didn't see much dirt/particles in the primary filter when I emptied it out, and the SCV's screen was clear, so must have been water. I'm hoping that I dodged a bullet and the injectors won't have any issues. The dealer ran the engine for like 5-10 min at idle and full throttle and it ran fine, but who knows. Yeah I'm gonna go on a leap here and say my local dealer does *not* have those tools!
Linking this back to a similar issue, which may help somebody in the future. Help! Troubleshooting Yanmar T175 Engine Codes and Derate Greetings, Was on a worksite (my first big job of clearing and grading 1 acre for a home build), when all of the sudden my compact track loader started to sputter stall intermittently now it seems to be permanently derating. Here are the codes that are coming up on the to 2018 Yanmar T175 with... HeavyEquipmentForums
I have the same engine in a sawmill. I have had intermittant issues with rpm fluctuating. Two years ago, I took it to a Yanmar dealer. No fault codes, but they found some water in the fuel tank. Since then I have removed the tank and replaced the filters, purged and bled the lines and kept sawing at any rpm fluctuations. Last June, I couldn't get it to stop losing 800-900 rpm fluctuating and took it back to the dealer. They changed the PRV (PLV) and cleaned the SCV. After getting the fuel pressure relief valve replaced and bringing it home and still having rpm sputtering after about an hour or so run time..........I took it back July 2nd. They removed the fuel injectors and sent them out for bench testing. They didn't get to them before the 4th weekend was over and Hurricane Beryl shut them down for a week. Injectors tested good. They said high pressure fuel pump was next in the shot gunning process. They got it from Bosch (at way less price than Woodmizer or Yanmar) with a one year guarantee. The 3 pumps that were supposed to be in Atlanta were not. So the pump came from Germany. They installed it and no help. They ordered new fuel injectors, thinking the springs in the injectors lose springiness (yes, that's a word) when heated up. The new injectors were no help and they are having verbal talks with Yanmar tech support. I still think this is a heat related electrical problem. But what do I know about Tier IVs? Oh yeah, in regen it runs normally, then the rpm goes back to fluctuating when out of regen. Also, they have bypassed the low pressure fuel system with no helping the problem. Any ideas???
Your engine equipped with EGR? EGR is shut off during regen. Wonder if you're not getting choked out with recycled exhaust gas.
I will text the dealer about the EGR. Thanks
Could it be an ecm issue, or perhaps a wiring fault between the computer and fuel pump? Are the rail pressure psi’s consistent? You can read them with the little engine monitor on the Woodmizer. (My 3tnv is on a Woodmizer as well). Not surprised the dealer is basically clueless. I had to do my own research and hold the technicians hand through the diagnosis process. They were only useful insofar as they had a computer and dongle that would connect to the dam thing.
My gut feeling was always a heat related electrical issue. Talked to the service manager this morning. They are thinking electrical now. They found a slight slip in voltage from the crankshaft sensor. Running now to verify. Presures spikes in relation to the rpm fluctuating. I have seen it spike to 21000 psi when rpm is dropping 800-900 rpm. I have mentioned the ECM to them, but they keep saying no fault codes or history. It is a Woodmizer LT40 HD Wide Woodmizer engine guru says it can be EGR issue or even intake obstruction.
Hey, Bindian. Been missing you on FForum! Hope all is well and you get the Yanmar squared away soon.
Thanks KenMac. Hurricane Beryl put me a week behind watching the Astros. I've been trying to catch up.
Got a vague text from the service manager stating the pipe, cross over tube connection plug and pins have been checked. I gather this relates to the EGR. Yanmar tech rep has them digging into electrical this week. Were doing a test run today.
Service manager called to say the Yanmar is fixed. It came down to replacing the crankshaft AND camshaft sensor. 42 hours troubleshooting, but he did me right and only charged 10 hours labor. Lots of this labor time was just monitoring the engine at high idle. At $155 an hour, I got a huge break. I pick it up tomorrow.
I'm glad you have some resolution to your issue! At least, I hope you do!
I sawed today. I got the sawmill home yesterday from the Yanmar dealer. I had two more 10 foot 8x8s to cut to finish an order. I was able to saw this one. Took the photo and took a break. Came back out to saw the side boards to width. Cranked up and it died. That has never happened before. Cranked it again and it died. I check for fault codes and have 10 codes. The good news is I have fault codes!!! P0183 P0201 P0193 P0627 P0337 P0122 P0336 U0292 U1293 U1303 The bad news is I have to take it back to the Yanmar dealer. Any idea what all the codes are? I only know P0627
Seems like a connector worked itself loose. That would be my first guess with all those codes happening simultaneously. Btw you can just google the codes, most obdii codes are universal
Thanks! I will search them on Duck Duck Go. I'm not a google fan
The P03xx lead to crank sensor, the others are rail sensor and #1 injector. As shared by John V, must be something worked loose. I would speculate a ground. Perhaps a grounding bolt wiggled out or a connector at the ECM was locked in perfectly. Glad to read the dealer whittled down the labor, but it should have lasted longer than a few hours. .
I found them all here............https://www.toro.com/getpub/212273 Maybe I won't have to haul it 50 miles back to them! Thanks! Will these codes clear themselves if I check all those connections? Or will it need to be hooked up to a Yanmar computer?
They will most likely just go inactive which is usually good enough.
Thanks. Gonna put it in the barn and check it tomorrow.
It was a loose connector to the ECM.
A little bargaining chip, to beat the service department with. Lol.
JohnV, Where did you buy your manuals?
I found them online, I can email them to you if you dm me your email
I was able to saw for 12.2 hours and the rpm started sputtering again. It's back at the engine shop.